Turner was born in Atlanta, Georgia, and attended public schools in Maryland. He received his B.A. from Washington and Lee University in 1954 and spent the 1954-1955 academic year as a Fulbright scholar at the University of Munich and the Free University of Berlin. In the fall of 1955 he began graduate study at Princeton University. He completed his M.A. in 1957 and his Ph.D. in 1960 under the supervision of Gordon A. Craig. Turner was hired by Yale University as an instructor in history in 1958. He was elevated to assistant professor in 1961, associate professor in 1964 and professor in 1971. From 1976 to 1979 he was chairman of the Yale History Department. During his career he held a number of endowed chairs in history at Yale and trained numerous graduate students in modern German history. From 1981 to 1991 Turner also served as Master of Davenport College, one of 12 residential colleges at Yale. He retired in 2002 as the Stillé Professor of History. His papers are housed in the Manuscripts and Archives Division of Sterling Memorial Library at Yale University. He died from complications from melanoma on December 17, 2008, at Yale-New Haven Hospital.

In his essay, "Fascism and Modernization" from the book Reappraisals of Fascism, following the arguments first made by David Schoenbaum, Turner argued National Socialism sought the total destruction of modern industrial society and its replacement with agrarian society where Germans obtain Lebensraum in Eastern Europe where German colonists would settle the land and reduce the Slavic peoples to the slaves. However to accomplish these goals, the Nazis forced despite the anti-modernist nature of their ideology to further modernize German society. Turner called Nazi anti-modernism a "double" form of utopianism in that it was a vision that was both impractical and unachievable.

Turner is best known for his book German Big Business and the Rise of Hitler, published in 1985. In it he rebutted the claim that it was German big business which primarily financed and otherwise promoted the attainment of power by Adolf Hitler. He argued that the extent of business support for Hitler and his Nazi Party had been much exaggerated. On the basis of careful examination of unpublished records of major German corporations and of Hitler's party, Turner concluded that the bulk of the Nazis' funds during their rise came from their party's members and other ordinary Germans and that the principal political recipients of big business funding were the traditional right-of-center parties, the German People's Party and the German National People's Party. The only election campaign in which big business contributed significant amounts of money to the Nazis was that of March 5, 1933, after they were already in power

In Turner's view, the Third Reich was a possible but by no means inevitable result of German history, thus leading Turner to oppose the Sonderweg thesis. He has contended that the acquisition of power by Adolf Hitler was heavily influenced by contingency and that military rule was a viable alternative to the Third Reich. In his 1996 book Hitler's Thirty Days To Power: January 1933, he maintained that it was the actions of a few individuals, such as German president Paul von Hindenburg and chancellors Franz von Papen and Kurt von Schleicher, which enabled Hitler to come to power through semi-legal means. Political incompetence and personal rivalry between Papen and Schleicher ultimately led to Hitler's being appointed chancellor of Germany by President Hindenburg on January 30, 1933, without ever having won a majority in a national election.

Turner's General Motors and the Nazis (2005) examined the history during the Third Reich of Adam Opel AG, the German subsidiary of General Motors.

In the early 1980s, Turner was one of the critics of the book The Collapse of the Weimar Republic by David Abraham, then an assistant professor of history at Princeton University. Abraham, a Marxist who received a Ph.D. from the University of Chicago for a dissertation that was the basis for his book, maintained that big business bore major responsibility for Hitler's rise to power. Turner, working on the same topic from a non-Marxist perspective, was familiar with the archives and documents cited by Abraham and challenged Abraham's use of evidence from those sources, which led to a controversy over erroneous citations, inaccurate quotations, and other misrepresentations in Abraham's book. In this effort Turner was seconded by Gerald D. Feldman, history professor at the University of California, Berkeley, who subjected Abraham's book to thorough scrutiny in a lengthy article in a scholarly journal. They were supported by a wide array of historians, including conservative Gertrude Himmelfarb and Marxist Timothy Mason. However, historians, including Arno J. Mayer, Carl Schorske, Thomas Bender, and Natalie Zemon Davis, came to Abraham's defense. They accused Turner, Feldman, and their allies of "fetishing" facts and attacked them for emphasizing "historical fact" over "historical imagination." Abraham was denied tenure at Princeton and eventually left the historical profession, later becoming a professor of law at the University of Miami.